Forge actuator opening rates

[liquidswords88]

I have a forge actuator bought from sportmachines. It came with the blue spring, which is 14-18lbs. I am doing some testing to see actual opening pressures. I use a very accurate tire pressure gauge to set an air tank to 15psi. I then take a blow gun and blow the 15psi into the actuator, it does not even think about moving. It does not start to move until 18psi. When it does move at 18psi the movement it maybe a 1/4 inch at most. Now when I put 25-30 pounds of pressure to it it moves out about an inch. I am not sure if the excess pressure will damage the unit or not, but that's how I have learned my whole life. I have been reading some stuff about the waste gate travel, and getting the puck to open more. I believe that it would help over boosting.

I am new to the turbo thing, so I am learning as I go here. Does 15lbs of boost mean that the turbo is putting out 15lbs? Or is some lost in translation? It seems like a dumb question, but how can this actuator provide me with 14-18lbs if at 14lbs of input it does not even flinch. I also noticed that there is an extreme amount of preload on the actuator when taking it apart. I consider myself a fairly strong dude, but I had to apply quite a bit of force to hold the cap on so I could get the screws started. Could I trim the spring to make it shorter so there would be less preload. I know that making the spring shorter would make it stiffer, but the preload just seems off to me. I do not understand why there so much travel in this thing but it only moves a tiny amount?

 

[liquidswords88]

Re: Forge actuator opening rates

I have been doing some research on this subject. I found a vw forum talking about the forge actuator. These guys were from Europe. It would seem to me that a portion of the world that has been using turbo cars in large amounts for many years would be a bit knowledgeable about these things. Anyways they said that for the forge units you want to use a spring that was approx half of your total boost. The actuator would be at full extension with double the input pressure of the springs rating. This all makes sense as I can fully extend my 14-18lb spring with 32-35 pounds of input air.

It seems that the heavy preload of the forge units is to prevent the waste gate from opening early due to weak spring pressure from the stock actuator. If my math is right you would want a spring pressure of around 7lbs to get a max extension from 14lb input.

If anybody cares I can post a screenshot of the page from the vw forum. I am having over boost issues with my ty. I do not have a catalytic converter, and I know that is prone to cause issues. I refuse to put one back on. I have seen more then two engines blow due to clogged cats. Until I can get the waste gate puck fully open and still have over boost I'm going to keep at it. Worst case I have to put a external waste gate in the crossover. I firmly believe that the over boost is caused by the puck not opening enough.

 

[jeepruby04]

Re: Forge actuator opening rates

There's more factors to consider. Exhaust pressure pushing against the puck, differential pressure before and after the throttle body, amount of heat soak the preload spring can absorb before it looses tension, type of boost controller (manual or electronic).
The actuator does more than just limit maximum pressure, it also helps to determine when and how boost is produced. Imagine extending the actuator rod so that the puck is always open just a little bit. Think of how slowly it would build boost like that. This is how a weaker spring will act.
Enlarging the waste gate hole or changing to a JSM style downpipe and exhaust housing may be better options.

 

[Davemc1963]

Re: Forge actuator opening rates

I have played around with my Forge actuator and it is a good unit. That said, if plumbed straight from the turbo as myself and most others do, it is just a mechanical device reacting to a pressure input, there will always be a slight delay in response. It has its limitations.
I run a modified stock turbo with a bigger compressor wheel and a ported wastegate. The gate is undersize for the application and even with the forge actuator fully open, it dosent open the wastegate fully. There has been debate about this and some as 'jeepruby04' has mentioned have managed to increase the CSA of the gate. However, we are where we are with a stock housing.
I tried the '10psi' spring and that is what it delivered. It drove fine, but I had to add a whole lot of preload to get the pressure up to run at 14psi.

With the higher spring back in and having adjusted to just holding the gate shut, it would overboost on the stock chip/tune. (On this subject however, I found my original 2Bar MAP sensor was reading high - compared to a calibrated gauge - something some may care to check out with a scanner/datalogger as this could be causing your overboost issues)
I have now fitted my Turbo tweak chip (and 3Bar MAP), and can now run happily at '15psi'. (same just shut preload) I still get occasional spikes, particularly if I have to let off the gas after a quick excursion, but it 'works' and runs better than it ever has. I would like to fit the softer spring again sometime and try and adjust the TT to try and control it using the boost solenoid, but at the moment, I'm just glad it runs pretty well. The TT chip makes the truck run so much sweeter! - cant recommend it enough. I do need to tweek it slightly, but its just time to do it and it runs better than it ever has untweeked!